FREE: Tidalis [Steam Key]

The listing, Tidalis [Steam Key] has ended.

Tidalis is a block-based puzzle game with casual appeal, hardcore depth, and an addictive new "streams" mechanic. The game is brimming over with riffs and variants on that core mechanic with 20 game modes, dozens of special blocks and items, and 115 levels in the adventure mode alone. The basic rules of the game are this: blocks fall down into the board and have a color and an arrow direction. If a stack of blocks exceeds the height of the board, you lose. In order to clear blocks, you must right-click and drag paths through the arrows to set up chain reactions of like-colored blocks.
If this sounds simple, that's because it is -- you'll be lining up lengthy chains within minutes. But you'll be surprised how much brainpower it takes to set up combos of multiple chains, and the many brainteaser-style puzzles include some real stumpers. Tidalis has co-op and competitive multiplayer modes (both online and offline); action-oriented modes and timer-less brainteasers; a lengthy, casual-friendly adventure mode; twenty unique game modes providing innumerable twists to the basic gameplay; dozens of special blocks and items; and over fifty minutes of beautiful music to go with the painterly art.
In short, several games' worth of content are built on top of this core mechanic, which you'll quickly find to be as iconic as it is novel.

More info: http://store.steampowered.com/app/40420/
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This game works on mac and linux too!

Good Luck!